The method that is suitable for you is the DCA method where you can invest a certain amount of money for a certain period. You can visit the Buy the DIP, and HODL! thread to learn it with us.

You can choose to invest your money every week or month to buy Bitcoin for 1 year or more. You must follow the plan you made to become a Bitcoin investor.

You don't need to worry about market movements because your focus is only on collecting Bitcoin little by little. So you just try to be patient and invest your money according to the plan you made.